In order to provide for maximum bone formation, it is desirable to transplant cells that already exhibit an osteoblastic phenotype, because such cells likely to exhibit bone-forming activity. However, in vitro differentiation of bone marrow stem cells into osteoblasts involves culturing in osteogenic medium (Jaiswal et al. 1997. J Cell Biochem 64: 295-312) and may lead to decreased proliferation of such cells in vitro. Moreover, the use of osteogenic medium involves addition of components to the cells (e.g., growth factors) that can have unintended side effects if those components are administered to a patient along with the cells.
Hence, there exists a need in the art for a simple and reliable method to produce osteoprogenitors, osteoblasts or osteoblastic phenotypic cells in vitro from stem cells, for example, human bone marrow stem cells, where the desirable cells are readily separated from the factors used for generating the osteoprogenitors, osteoblasts or osteoblastic phenotypic cells.